Means for qualifying the head space of firearms



Dec. 6, 1955 w. R. KUNZ 2,725,614

MEANS FOR QUALIFYING THE HEAD SPACE OF FIREARMS Filed June 9, 1952 2 Sheets-Sheet 1 IN V EN TOR.

W. R. KUNZ Dec. 6, 1955 MEANS FOR QUALIFYING THE HEAD SPACE OF FIREARMS 2 Sheets-Sheet 2 Filed June 9, 1952 l INVENTOR. W%; 11EL1TLR K.1ILZ

ATTGENE Y5 MEANS FOR QUALIFYING THE'HEAD SPACE F FIREARMS William R. Kunz, Springfield, Mass assignor to the United States of America as represented by the Secretary of the Army Application June-9, 1952, Serial No. 292,601

3 Claims. (Cl; 291.1) (Granted under Title 35', U. S.-C0de (1952), sec. 266) The invention described herein may be manufactured and used by or forthe Government for governmental purposes without the payment to me of any royalty thereon.

This invention relatesto the assembly of firearms and is more particularly directed to an improved method and means for qualifying the head space in small arms.

The head space in firearms is the distance from the base of the cartridge fully seated in the bullet chamber to the face of the bolt in battery position and is an important factor in the assembly of firearms because improper adjustment may cause serious malfunction of the firearm.

In some types of firearms, adjustable means are provided by which the head space may be qualified. However, in such weapons as the U. S. rifle, cal. .30 M1, the proper head space is attainable only by modifying the bullet chamber andisaccomplished by increasing the distance from the first shoulder in the bullet chamber to the breech end of; the barrel through reaming the aforementioned shoulder and so permit the bullet to seat deeper into the chamber and farther from the bolt. Therefore, in the manufacture of new barrels for such firearms, itis planned to have the depth of the beforementioned shoulder on the shallow side as a tight head space may readily be increased by the reaming thereof but too great a head space cannot, for'practical purposes, be corrected.

It is readily apparent, therefore, that in the manufacture of new rifles,- as well as the overhaul of used ones or whenever a barrel, a receiver, or a bolt is replaced, the qualifying of. the head space is an important part of the assembly operations. It is also obvious that with the expedience necessaryin modern production the qualifying operation should be assimple and: rapid as possible.

Present method and means require a number of mechanical and gaging operations with a plurality of tools and gages each of which, it is obvious, requires time for handling alone. Moreover, the present reamer and the means by which it is engaged" requires the reaming to be performed from the breech end of the barrel. To accomplish this the reamer must be engaged by universally jointed rods introduced through the opening in the under part of the receiver. Furthermore, the barrel and receiver assembly has to be turned several times in the retaining vise as the reaming operation, be-

cause of the aforementioned reason, is more conveniently performed with the lower part of the receiver upwards, while in the gaging operations. and the working of the bolt the receiver is best in its normal position.

Accordingly, it is an object of this invention to provide means which will simplify and expedite the qualification of the head space in firearms requiring modification of the bullet chamber.

It is another object. of, this invention to provide means for qualifying the head space in firearms wherein the nitcd States Patent "ice number of operations and tools presently required will be drastically reduced.

It is still another object of this invention to provide an improved means of qualifying the head space in firearms which is particularly adapted to be performed by unskilled operators.

It is a further object of this invention to provide an improved fixture for holding a firearm barrel and receiver assembly during the reaming operation required for head space qualification.

Still another object of this invention is to provide a power-driven reamer for use in the qualifying of firearm head space.

It is another and still further object of this invention to provide means of driving the reamer from the muzzle end of the barrel.

It is a specific object of this invention to provide means of qualifying the head space in firearms of the type of the U. S. rifle, cal. 30 M1.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is an elevational view showing a barrel and receiver assembly mounted in the holding fixture of the present invention;

Fig. 2 is an enlarged elevational view of the barrel and receiver assembly showing the relationship between the face of the bolt and the qualifying reamer immediately prior to the cutting operation thereof; and

Fig. 3 is a view of the qualifying reamer in partial crosssection.

As shown in Fig. 1 the fixture of the present invention, which. is particularly adapted for qualifying the head space in the: U. S. rifle, cal; .30 M1, is provided with a box frame 3' inclosing a suitable. electrical motor 2. Mechanically associated with motor 2 is a gear reducer unit 4 of conventional, construction provided to transfer the rotary action of motor 2 from a horizontal to a vertically disposed axis, and at a reduced rate of speed.

Extending upwardly from the top of frame 3V is a tubular member 5 and: is suitably secured. thereto as by a flange 6. In the upper extremity of tube 5 there is provided a substantially U-shapedcut out portion 7 and anoppositely disposed smaller cut out portion 8 of similar construction, both extending downwardly from the extreme edge thereof.

Suitably secured in the lower portion of tube 5, is a ring-like guide member 9. Extending upwardly within tube 5 is a shaft 10 having suitable means at the lower end thereof for engaging gear reducer 4 so as to be; rotated thereby. At the upper end of shaft it! are provided, four projecting ratchet type teeth 11 for a purposee to be shown.

Referring particularly to Fig. 3, there is shown; a longitudinally fluted reamer 12 having a tapered cuttingportion 13 suitable for finish reaming the countersunk. portion of a circular hole. Projecting axially from portion, 13 is a rod portion 14 v whichacts as a pilot for reamer 12. Rod 14 terminates in four circumferentially disposed ratchet type teeth 15 which mate with teeth 11 and thereby serve to rotate reamer 12 when shaft 10 is rotated.

At the opposite end of reamer 12 is a threaded portion 1.6 of smaller diameter than the fluted portion. On threaded portion 16 are mounted a locking nut 17 and, an adjustingmernber ltthaving a threaded longitudinal hole partly therethrough from one end to receive. portion 16. Provided at the opposite end of member 18 is a projecting head portionlfi of smaller diameter than the body portion thereof. Transverse holes 29' and 21 are provided'i'n nut 17 and adjusting member 18 respectively to. receive a drift or other suitable tool in order to provide manual rotation thereof.

As is well known, the cal. .30 Ml rifle is provided with a-. receiver 22 to which a barrel 23 is threadably secured, and in which a bolt 25 is slidably mounted. Barrel 23 is provided with a bore 28 and a chamber section 26 having an angular shoulder 27. Provided on the forward end of bolt 25 is a lug 29 which helically rotates over an arcuate surface 32 into a recess 39 in receiver 22 and thereby holds bolt 25 in locked battery position.

The diameter of reamer 12 is approximately that of the body of chamber section 26, while the angle of cutting portion 13 corresponds to that of shoulder 27 The diameter of rod portion 14 is slightly less than that of bore 28 and head portion 19 is of similar diameter to the head of the particular cartridge employed.

Adjusting member 18 is so adjusted that when reamer 12 is placed in chamber 26, as shown in Fig. 2, the distance from the face of head 19 to shoulder 27 is slightly more than the minimum dimension allowed for the head space of the weapon but considerably less than the maximum dimension. After the adjusting member 18 has been rotated to the desired position, locking nut 17 is rotated to contact one end of member 18 and thereby lock it in place.

By the method of this invention, the operator holding a barrel and receiver assembly 24 in one hand will install reamer 12 in the bullet chamber of barrel 23 with the other. Bolt 25 is next inserted into receiver 22 and is held with thumb 31 of the free hand pressing forwardly and downwardly on lug 29. If lug 29 cannot be fully seated in receiver recess 30, as shown in Fig. 2, it is apparent that the head space of the weapon is too small and therefore, must be qualified in the manner hereinafter described.

Still pressing lug 29 forwardly and downwardly by thumb 31, the operator will proceed to qualify the head space by placing the barrel and receiver assembly 24 downwardly in tube muzzle end first, with shaft extending upwardly through bore 28. As barrel and receiver assembly 24 is allowed to slide downwardly over shaft 10, barrel 23 passes through guide member 9 and becomes centered thereby. The downwardly projecting portion of receiver 22 is received by cut out portion 8 to be secured against rotation by the walls thereof with the lug 29 being pressed by thumb 31 through cut out portion 7.

Also, as barrel and receiver assembly 24 moves downwardly in tube 5, shaft 10 which is rotated by means of motor 2 through gear reducer 4, becomes engaged to reamer 12 by teeth 11 engaging teeth and thereby provides similar rotation to reamer 12.

As the operator presses downwardly on lug 29, bolt 25 is moved forwardly against rotating reamer 12, causing cutting portion 13 to act against shoulder 27. This reaming action obviously will continue until lug 29 becomes fully seated in receiver recess 30 at which point the pressure against reamer 12 is relieved and the cutting stopped. This takes only a few seconds as 10 or 12 turns of reamer 12, which is being rotated at approximately 56 revolutions per minute, are generally suflicient to ream shoulder 27 the proper amount.

When lug 29 is fully seated, the operator immediately removes barrel and receiver assembly 24 from tube 5, removes therefrom bolt 25 and reamer 12, and after proper cleaning of the parts sends barrel and receiver assembly 24 and the presently mating bolt 25 along the production line. It is important that the distance from cutting portion 13 to the face of head portion 19 be checked by the operator often enough, using a step gage or other suitable gaging means, to prevent using a reamer 12 that is out of tolerance as reamer 12 also serves as a gaging means in the method of this invention. When reamer 12 is worn beyond allowable tolerance, or requires resharpening, cutting portion 13 will be reground and adjusting member 18 reset.

If lug 29 can be fully seated in receiver recess 30 before any reaming takes place it shows that the head space is sufliciently large and does not need to be qualified. However, the head space must be checked to see if it is too large. This will be done by the conventional method of chambering the maximum head space gage provided for the weapon. If lug 29 cannot be fully seated with the maximum gage in chamber 26 the head space is within acceptable tolerances. If lug 29 can be fully seated, the head space is too great and further steps to be taken will follow conventional procedure.

The advantages of the present invention are obvious from the above description. The tools and gages, required to be handled by the operator, have been considerably reduced, saving operational time. It is also clearly apparent that this invention does not require special skill on the partof the operator or the exercise of judgment. Furthermore, inasmuch as the reamer is driven from the muzzle end of the barrel the necessity for universally jointed rods which are awkward to handle is eliminated. The advantages of motorizing the operation are obvious as are also those obtained by securing the barrel and receiver assembly without the need for a vise, which requires time for tightening and loosening.

The greatest advantage of this invention lies in the novelty of using the weapons bolt as the means of determining its own head space, one result of which is to give the qualifying operations an exactness not achieved before. Moreover, the adjustability of the qualifying reamer, and the method of using it also for gaging purposes, elirninates a number of tools and operations.

I claim:

1. Means for qualifying the headspace in a firearm of the type wherein the counter-recoil stroke of a reciprocal bolt drives a cartridge into the firing chamber of the barrel, said means comprising a reamer having a conical cutting portion insertable into the firing chamber from the breech end of the barrel, a cylindrical member adjustably secured to the rear end of said reamer so as to cooperate therewith in providing a predetermined distance measured between the origin of said reamer cutting portion and the rear end of said member, and means for rotating said reamer while the bolt is being moved forwardly in abutment with the rear end of said cylindrical member whereby said cutting portion of said reamer increases the depth of the firing chamber in the barrel to the extent necessary to permit the complete chambering of a cartridge without interfering with movement of the bolt into locked battery position.

2. Means for qualifying the headspace in a firearm of the type wherein a barrel is fixedly secured to a receiver and a bolt is reciprocably mounted in the receiver to drive a cartridge into the firing chamber of the barrel and against a conical shoulder therein, said means comprising a fixture for holding the receiver with the muzzle end of the barrel extending downwardly, a reamer having a conical cutting portion insertable into the firing chamber from the breech end of the barrel and adapted to seat against the conical shoulder in the firing chamber, a cylindrical member having a rear end engageable with the front face of the bolt, means for adjustably securing said cylindrical member to the rear end of said reamer so as to project rearwardly from the firing chamber when said reamer cutting portion is fully seated therein against the conical shoulder, a rotating shaft insertable into the muzzle end of the barrel, and means for engaging said shaft with said reamer to impart rotation thereto whereby the continued forward movement of the bolt following the engagement thereof with the rear end of said cylindrical member advances said reamer cutting portion to increase the distance from the conical shoulder in the firing chamber to the breech end of the barrel until completion of the movement of the bolt into fully locked battery position.

3. Means for qualifying the headspace in a firearm of the type wherein the counter-recoil stroke of a reciprocal bolt drives a cartridge into the firing chamber of the barrel and against a conical shoulder therein, said means comprising a reamer having a rearwardly projecting threaded stud and a forwardly projecting rod portion terminating in a plurality of ratchet teeth, said reamer having a conical cutting portion insertable into the firing chamber from the breech end of the barrel and adapted to seat against the conical shoulder therein, a cylindrical member threadably mounted on said rearwardly projecting stud of said reamer, means for adjustably locking said member on said stud in a position providing a predetermined distance measured between the rear end of said reamer cutting portion and the rear end of said member, a shaft extending into the barrel from the muzzle end thereof and having a plurality of ratchet teeth 15 on the terminal end thereof engageable with said ratchet teeth on said rod portion of said reamer, and means for rotating said shaft to impart similar rotation to said reamer whereby movement of the bolt into fully locked battery position engages the rear end of said cylindrical member and thereby advances said reamer into cutting engagement with the conical shoulder in the firing chamher to increase the distance therefrom to the breech end of the barrel for permitting the complete chambering of a cartridge in the barrel without interfering With movement of the bolt into locked battery position.

References Cited in the file of this patent UNITED STATES PATENTS 530,823 Couch Dec. 11, 1894 530,824 Couch Dec. 11, 1894 2,429,375 Smith Oct. 21, 1947 2,587,519 Peirce Feb. 26, 1952 

